Patent GB-396210-A (GB)
Title: Improvements in or relating to electric lamps
IPC: H01J61/96
Filed: 1932-06-18
Abstract: 396,210. Discharge lamps. SPERTI LAMP CORPORATION, 250, Park Avenue, New York, U.S.A.-(Assignees of Sperti, G. ; Covington, Kentucky, U.S.A.) June 18, 1932, No. 17293. Convention date, Oct. 31, 1931. [Class 39 (i).] An electric lamp embodying a source of visible radiation combined with,a source of ultra-violet radiation comprises a bulb having an outer chamber containing an incandescent filament, and a sealed inner chamber containing ionisable material and arc electrodes which have electronemitting surfaces and are provided with heating filaments which are shielded from the arc and are connected in series with' the incandescent filament. The lamp bulb 1, Fig. 2, which may consist of quartz glass or the glass known under the registered Trade Mark " Corex " is provided with a stem 4 supporting the inner bulb 13 which may consist of any known ultra-violet transmitting glass provided with an external filter 15 which absorbs substantially all wave lengths shorter than about 2950 Angstrom units, a thin sheet of mica, or a coating of a transparent varnish, such as a cellulose varnish, providing a suitable filter. The filtering device may be either on the inside or outside of the bulb 13. Wires 11 radiating from the top of the inner bulb support the incandescent filament 9, the ends of the filament being supported by two wires 6, 10 which are fused into the stem, the wire 6 being connected to one of the leading-in wires of the lamp. A wire 24 connected to the end of the filament at the top of the support 10 connects the filament in series with electrode heater filaments 22, 23 which are connected in series by a conductor 25, the outer end of the heater 22 being connected to the leading-in wire 7. The electrodes consist of metal sleeves 16, 17 coated with an oxide or a mixture of oxides of materials such as strontium, barium, &c., and supported by means such as bands 18, 19 on supports 20, 21 fused in the walls of the arc chamber. The electrode 16 is connected by a wire 27 to the leading-in wire 7, and a conductor 28 connects the electrode 17 to the wire 24. To increase the potential drop between the electrodes a resistance 29, which may also become incandescent is connected between them in the conductor 25. The oxide coating on the electrodes may be protected by grids or shields in the form of flat coils 31, 32, or wire mesh screens, which are supported by the .electrodes and electrically connected thereto. In a modification the electrodes are disposed parallel to one another and consist of tubes 45, Fig. 3, of insulating material such as quartz glass surrounded by sleeves 46 of nickel or the like, preferably coated with oxides of strontium or barium &c. The electrodes are supported by bands 47 welded to wires 48 fused in the stem 49 of the inner bulb. Protecting grids 50 consisting of coils of tungsten wire are preferably provided around the electrodes. The electrode heater-filaments 54, 56 are connected in series by a resistance 55 which is disposed within the bulb 13 and may be protected from the heat of the arc by coating it with alundum, or enclosing it within a quartz glass tube of inverted U-shape, the limbs of which comprise the quartz tubes 45. The arc chamber 13 contains an ionisable material such as a small quantity of mercury, or neon or like gases, with or without the addition of mercury may be employed. The bulb 1 may be filled with an inert gas such as nitrogen, argon, &c., at a relatively high pressure. Either the inner or the outer bulb may be frosted.